Question

The oxidation state of $Mn$ in $K_{2}Mn{O}_4$ is

• A. +2
• B. +7
• C. -2
• D. +6

Answer 1

The correct option is D

+6

The oxidation number of oxygen is -2 in most of its compounds , except in peroxides like $H_2{O}_2,Ba{O}_2$ etc. where it is -1

1.Another interesting exception is found in the compound$O{F}_2$ (oxygen difluoride) where the oxidation number of oxygen is +2

2.This is due to the fact that fluorine being the most electronegative element known has always an oxidation number of -1.

3. In compounds formed by union of metals with non-metals, the metal atoms will have positive oxidation numbers and the non-metals will have negative oxidation numbers.

4. The oxidation number of alkali metals ($Li,Na,K$ etc.) is always +1 and those of alkaline earth metals ($Be,Mg,Ca$ etc) is +2.

Therefore, O. N. (O) =-2

O.N. (K) =+1 (alkali metal)

$K_{2}Mn{O}_4⟹$ 2$\times$(1) + n - 2$\times$(4) =0

n = 8 - 2 = +6

So, oxidation state of $Mn$ is +6.